Automatic transfer switch control circuit



w w W Y R S E 0 T N I M R m y u E m T u mm W O M r u .I. R

mm mmm L wm 1.

mm NC Lam} ium m May 15, 1956 AUTOMATIC TRANSFER SWITCH CONTROL CIRCUITv P o 3 a g Pm m2. uzj

United States Patent AUTOMATIC TRANSFER SWITCH CONTROL CIRCUIT LoydJames Robertson, Albuquerque, N. Mex. Application December 6, 1951,Serial No. 260,239 9 Claims. (Cl. 30764) The present invention relatesto an automatic control for connecting a load to a main supply ofelectric current when main and auxiliary supply sources are provided andfor connecting the load to the auxiliary source in the event the mainsource fails.

Although it has been proposed to shift a load from one supply line toanother in the event of failure of one line, these proposed arrangementshave been deficient in a number of features. Prior control systems havebeen unnecessarily complicated and in many cases have unnecessarilyshifted the load from one supply line to the other when the break wasmomentary. Further, the prior control systems did not include indicatingmeans to show which line was furnishing the power. Also the switchoperating means of the prior art required continuous energization of theactuating mechanism, and the switch arrangements of some prior systemscould connect both lines to the load at the same time.

It is therefore an object of the present invention to avoid the defectsof the prior art and produce a new and useful control circuit.

Another object of the present invention is to provide a control forconnecting only one of two separate sources of electricity to a load.

A further object of the present invention is the provision of a controlfor two supply lines for a single load with the supply of current fromone line normally connected to the load but in the event of failure ofpower in the one supply line the current will be automatically suppliedby the other supply line. Also upon the return of power to the said oneline, the load will be auto matically reconnected thereto.

Another object of the present invention is the provision of a time delaybetween the interruption of the supply of current from one line and theconnection of the load to the other line so that unnecessary changesfrom one supply line to the other are avoided.

Further and other objects will appear as the description proceeds andupon reference to the drawing showing a wiring diagram of an embodimentof the present invention with the connections arranged for the supply ofpower from the main supply.

Only one wire is shown for each supply line A and B and the load C sinceit is well understood that the other wire in the usual two wire systemsis normally grounded, and the showing of the other normally groundedwire in the diagram would result in unnecessary complications withoutattendant advantages.

The supply lines A and B represent the usual main and auxiliary supplylines such as are used for supplying a rural district from two separatesources. The load is represented by a third line C which is connected toone of the supply lines by the solenoid actuated main switch 10.

A main switch serves to connect supply lines A or B to the load C. Thisswitch includes a contact A2 connected by lead A1 to main supply line A.Contact A3 is connected by lead A4 to lead L1 to the load C.

Similarly auxiliary supply line B is connected by lead B1 to contact B2.Contact B3 spaced from E2 is connected by lead B4 to lead L1 which inturn is connected to load C. Switch 10 includes bridging contact 11 and11' mounted on solenoid armatures 12, 12' respectively which areactuated by solenoids 13, 13 respectively. Armatures 12, 12' areconnected by lever 14 which is pivoted intermediate its ends at 15 andis connected at its ends to armatures 12, 12 by suitable means such aspin and slot connections 16 and 16 respectively. Contacts 11, 11 provideelectrical connection between contacts A1, A2 and B2, B3 respectivelyand only one supply line may be connected to the load and at one time.

Line A is also connected by means of lead A5 to an insulated contact A6on an armature 17 of a relay B-ll. Contact A6 is urged by the usualspring into engagement with contact A7 connected by means of lead A8 torelay A-ll. The circuit is completed to a ground from relay A41. Thisenergization of relay A-11 causes armature A9 thereof to assume the fullline position against the tension of the spring and into contact withthe contact 18. Armature A9 is connected by lead 2 4 to conductor 25thence by lead 26 to the positive terminal of battery 27. Contact 12through lead 19 is connected to motor timer M1; from motor timer M1 alead 28 is connected to Contact 21 of single pole double through switch22. A spring normally urges the moveable element 22.- of switch 22 intoengagement with contact 35 and the moveable element 23 is moved intoengagement contact with 21 by an extension 45' of lever 14 which engagesthe moveable element 23. In the event that main switch iii is in fullline position the circuit from contact 21 would not be completed and nochange would occur since the supply or" current to the load is alreadycoming from main supply line A.

In the above example, in the event that main switch 10 was in the dottedline position, the circuit from contact 21 would be completed throughmoveable element 23 and ground. This would cause motor timer M2 to beginoperating thereby rotating the gears in the gear train and causing arm28 to engage a normally open switch 29, closing the same andestablishing a connection from ground through lead switch 29, lead 31,to relay 32 and from relay to lead 36 thence to conductor 25 and lead 26to the battery. This resulting energization of relay 32 causes armature33 to establish contact with contact 4-2 for supplying current from thebattery through lead 26, conductor 25, lead 36, contact 92, armature 33,lead to solenoid l3 and from thence to ground. This energizes solenoid13' causing armature 12 to move from the dotted line position to thefull line position carrying bridge contact 11' away from contacts B2 andbridging the connection from line B to load C. Due to the leverconnection 14 between armatures 12. and i2, armature 12 carrying bridgecontact 11 is moved from the dotted line position to the full lineposition establishing electrical connection between contacts A2 and A3resulting in main supply line A furnishing electricity to load C. Whenlever 14 is moved from the dotted line to the full line positionarmature 23 of switch 22, moves from the dotted line to the full lineposition because of the spring bias thereof breaking the circuit throughlead to motor timer M1. Upon deenergization of motor timer Mt a spring41 moves arm 28 away from switch 29 breaking the circuit anddeenergizing relay 32. From the above description the normal operationof the circuit for supplying current from main supply A to the load C isdisclosed.

In the event that supply line A fails, current will no longer besupplied to relay A-Il thereby releasing armature A9 for movement to thedotted line position which it would assume, due to the conventionalspring. Current is supplied from the battery through lead 26, conductor25 and lead 24 to armature A9 of relay A11 and thence through lead 43 tolead 39 to motor timer M2. From motor timer M2 the circuit is completedthrough lead 40 to contact 35 of switch 22 and thence to groundedmoveable element 23 since the prior condition had the switch in the fullline position. The actuation of motor timer M2 causes the gear train tooperate and move arm 28 into engagement with normally open switch 29. Acircuit is established from ground through lead 30' switch 29', lead 31'to relay 32 and from relay 32 through conductor 25 and lead 25 to thebattery 27. The resulting energization of relay 32' causes armature 33'thereof to complete a circuit from the battery 27 through lead 26conductor 25 contact 42' armature 33' lead 34' to solenoid 13 forenergizing solenoid 13 causing armature 12 to move from the full lineposition to the dotted line position causing bridge contact ii to breakthe circuit from A2 to A3 interrupting the connection from main line Ato load C. Due to the lever 14 connecting armature i2 and 12, the bridgecontact H is moved to complete a circuit from contact B2 to contact B3resulting in supplying electricity from auxiliary line B to load Fromthe above description it is believed to be clear that electric currentis normally supplied from main line A to the load, but in the event offailure of main supply line A, power will be supplied from auxiliaryline B until the supply of power is restored to line A. As soon as poweris restored to line A the relay A11 will be energized to cause the loadC to be connected to the main line.

In the event that it is desired to have supply line B become the mainsource of power and supply line A become the auxiliary source, themanual switch B5 is closed carrying the current from line B through leadB5 switch B6 to relay B-ll thence to ground. The resulting energizationof relay B-lll causes armature 17 to move to the dotted line positionthereby making a circuit from battery 27, through lead 43, armature 17,contact 37, and leads 38 and 39, to motor timer M2, and therefromthrough lead 40, to contact 35, of switch 22, to armature 23, and toground thereby causing operation of the motor timer and the gear trainto move arm 28' into engagement with switch 29', for closing the same.The closing of switch 29 establishes a circuit from ground through lead30', switch 29, lead 31', to relay 32', and from relay 32', to conductor25 and lead 26 to the battery 27, thereby energizing solenoid 32.Armature 33' of relay 32 moves into engagement with contact 43' andcompletes a circuit from the battery 2'7, through lead 26, conductor 25,contact 42', armature 33', lead 34', to solenoid l3 and thence to groundthereby causing armature 12, to move from the full line position, to thedotted line position. This causes the extension 45 of lever 14 to engagemoveable element 23 to break the contact between contact 35 and groundedarmature 23, thereby deenergizing the motor timer M2 and permittingspring 41' to turn the timer to the position shown. The lever 14 alsocauses armature 2 to move bridge contact 11 into circuit closingengagement with contacts B2 and B3, establishing an electricalconnection between line B and the load C. I

It is believed to be clear that when switch B6 is closed the power issupplied from line B under normal circumstances, but in the event offailure of power in line B, relay B-lll will be deenergized allowingarmature 17 to assume its full line position resulting in thearrangement described in the first condition, a description of thecircuit is not repeated as the operation should be clear.

An additional feature of this control includes indicating lamps A49 andBlii connected to the battery by common lead 41, conductor 25 and lead25. Lamp A-lil is connected by lead 44 to lead 49 to contact 35 andgrounded moveable element 23 thereby completing a circuit resulting inthe illumination of lamp A-ltl which indicates that the power issupplied by line A. Lamp 13-11 is similarly connected by lead 46 to lead20. When main switch 10 is in dotted line position as would be the casewhen line B was supplying the power, contact 21 of switch 22 makescontact with moveable element 23 and completes the circuit from lead 20to ground illuminating lamp B10. The indicating lamps would bepositioned at any suitable location which could be spaced a substantialdistance from the main switch 10 making it a simple matter for thesub-station attendant to be informed of the line supplying the electricpower.

It appears that the advantages of the present control system are obviousand that the consumer has the choice of determining which line willnormally supply the power requirements. In the event of differences inrates on difierent lines it may be desirable to change the main supplyfrom one line to the other and vice-versa. Also due to the differentdemand conditions on the diiferent supply lines it is advantageous forthe consumer to have the control of which power lines supplies the load.

The motor timers M1 and M2 do not operate instantaneously and thereforeallows a small delay between the actuation thereof and the closing ofthe switches 29 and 29. This is a substantial advantage because it doesnot change the supply lines when momentary failures occur as when theline is struck by lightning. However, if the delay is of suflicientduration the load is connected to the supply line having availablepower. If both lines of power fail, the load will be connected to line Bas both relays B-11 and A-ll will be deenergized.

It is contemplated that the extent of time delay may be controlled bythe type of springs 41, 41 used for returning the motor timers to theirfull line deenergized positions; also the gear ratio on the motor timerscould be varied and other suitable means such as brakes, dashpots or thelike could be used for controlling the time delay. Relays A-11 and B--11may be connected to the secondary of transformers to avoid having thefull line voltage in the control circuits thereof.

It will be obvious to those skilled in the art that various changes maybe made in the invention, without departing from the spirit or scopethereof, and therefore the invention is not limited by that which isshown in the drawing and described in the specification but only asindicated in the appended claims.

What is claimed is:

l. A control system for the selective connection of a load to a main oran auxiliary power line comprising a main switch including a contactconnected to the main line, a second contact connected to the auxiliaryline, third and fourth contacts connected to the load, a first solenoid,a first armature movable thereby, a bridging contact on said armaturemovable to close the circuit between said first and third contacts, asecond solenoid, a second armature movable thereby, a second bridgingcontact on said second armature movable to close the circuit betweensaid second contact and said fourth contact, interconnecting lever meansbetween said first and second bridging contacts for causing saidbridging contacts to be in operative position one at a time, said leverhaving an extension at one end thereof, a single throw double polespring biased limit switch located in the path of the extension of saidlever means, said limit switch being closed in the spring biaseddirection when said first bridging contact is in circuit closingrelation and said limit switch being closed in the opposite directionupon contact by the extension of said lever means when said secondbridging contact is in circuit closing relation between said auxiliaryline and said load, a first relay in said system normally connected tosaid main line, a second relay connectable to said auxiliary linethrough a manually operated switch, the armature of said second relayhaving a spring biased insulated contact connected to said main line tocomplete a circuit to said first relay,

an independent source of electrical energy, first and second motortimers, said energy source, a first contact of said first relay, saidfirst motor timer and the contact of the normally closed contact of thespring biased single pole double throw limit switch being in a circuitwhereby the first motor timer is actuated when all of these contacts areclosed; a normally open switch actuatable by said first motor timerafter a predetermined delay, a third relay actuatable by said normallyopen switch, a contact of said third relay being closed when the latteris actuated for operating said second solenoid, a second contact of saidfirst relay being closed when said first relay is deenergized and beingconnected to a contact of said second relay which is closed when saidsecond relay is energized and said contacts being connected together andto said second motor timer, said second motor timer being connected tothe contact of said limit switch which is normally spring biased closed,whereby said second motor timer may be actuated, a second normally openswitch actuatable by said second motor timer after a predetermineddelay, a fourth relay connected to said second normally open switch, acontact of said fourth relay being connected to said second solenoid foractuating the second solenoid and establishing a connection between saidauxiliary line and said load when the power of said main line fails orsaid manual switch is operated, and electrically operated indicatingmeans connected to said independent source of electrical energy and tosaid single pole double throw limit switch for indicating the positionof said main switch.

2. A control system for the selective connection of a load to a main oran auxiliary power line comprising a main switch including a contactconnected to the main line, a second contact connected to the auxiliaryline, third and fourth contacts connected to the load, a first solenoid,a first armature movable thereby, a bridging contact on said armaturemovable to close the circuit between said first and third contacts, asecond solenoid, a second armature movable thereby, a second bridgingcontact on said second armature movable to close the circuit betweensaid second contact and said fourth contact, interconnecting lever meansbetween said first and second bridging contacts for causing saidbridging contacts to be in operative position one at a time, said leverhaving an extension at one end thereof, a single throw double polespring biased limit switch located in the path of the extension of saidlever means, said limit switch being closed in the spring biaseddirection when said first bridging contact is in circuit closingrelation and said limit switch being closed in the opposite directionupon contact by the extension of said lever means when said secondbridging contact is in circuit closing relation between said auxiliaryline and said load, a first relay in said system normally connected tosaid main line, a second relay connectable to said auxiliary linethrough a manually operated switch, the armature of said second relayhaving a spring biased insulated contact connected to said main line tocomplete a circuit to said first relay, an independent source ofelectrical energy, first and second motor timers; said energy source, afirst contact of said first relay, said first motor timer and thecontact of the normally closed contact of the spring biased single poledouble throw limit switch being in a circuit whereby the first motortimer is actuated when all of these contacts are closed; a normally openswitch actuatable by said first motor timer after a predetermined delay,a third relay actuatable by said normally open switch, a contact of saidthird relay being closed when the latter is actuated for operating saidsecond solenoid, a second contact of said first relay being closed whensaid first relay is deenergized and being connected to a contact of saidrelay which is closed when said second relay is energized and saidcontacts being connected together and to said second motor timer, saidsecond motor timer being connected to the contact of said limit switchwhich is normally spring biased closed, whereby said second motor timermay be actuated, a second normally open switch actuatable by said secondmotor timer after a predetermined delay, a fourth relay connected tosaid second normally open switch, a contact of said fourth relay beingconnected to said second solenoid for actuating the second solenoid andestablishing connection between said auxiliary line and said load whenthe power of said main line fails or said manual switch is operated.

3. A control system for selectively connecting a main line or anauxiliary line to a load comprising a main switch operatable to connectsaid main line and auxiliary line one at a time to the load, a firstsolenoid for moving said main switch to connect said load to said mainline, a second solenoid for actuating said main switch for connectingsaid auxiliary line to said load, a first relay energized by said mainline, a single pole double throw limit switch actuatable by said mainswitch for making a contact when said main switch is in either position,a first motor timer connected in series with one contact of said limitswitch, said first motor timer being actuated when said first relay isin the energized position, a first normally open switch operated by saidmotor timer for energizing said first solenoid connecting said main lineto the load, a second motor timer in series with the other contact ofsaid limit switch, said second motor timer being actuated when saidfirst relay is in deenergized position, a second normally open switchoperated by said motor timer for energizing said second solenoidconnecting said auxiliary line to the load.

4. A control for selectively connecting a load to a main or an auxiliarypower line comprising a main switch connectable to said load and one ata time to said main and auxiliary power lines, a first solenoid foractuating said main switch to connect said main line to the load, asecond solenoid for actuating said main switch to connect said auxiliaryline to said load, a first relay connected to said main line, a firstmotor timer actuatable by said first relay for momentarily energizingsaid first solenoid for connecting said main line to said load, a secondmotor timer actuatable by said first relay when said main power line isdeenergized for momentarily energizing said second solenoid forconnecting said auxiliary line to said load.

5. A control system for selectively connecting a main or auxiliaryelectric power line to a load comprising a main switch operative toconnect said main and auxiliary lines one at a time to said load,electric means for actuating said switch, means responsive to theenergization of said main line for causing said electric means tooperate said switch to connect the main line to the load and upondeenergization of the main line causing said switch to connect saidauxiliary line to the load, and timing means actuated by thedeenergization of said main lines for delaying the operation of saidelectric means whereby a momentary interruption of the energization ofsaid main line will not cause said electric means to operate, andindicating means controlled by the positions of said main switch to showwhich electric power line is connected to the load.

6. A control system for selectively connecting a main or auxiliaryelectric power line to a load comprising a main switch operative toconnect said main and auxiliary lines one at a time to said load,electric means for actuating said switch, means responsive to theenergization of said main line for causing said electric means tooperate said switch to connect the main line to the load and upondeenergization of the main line causing said switch to connect saidauxiliary line to the load, and timing means actuated by thedeenergization of said main line for delaying the operation of saidelectric means whereby a momentary interruption of the energization ofsaid main line will not cause said electric means to operate.

7. A control system for a main and auxiliary supply line for supplyingelectric current to a load comprising a 7 main switch arranged when inone position for connecting the main supply to the load and when in theother position connecting the auxiliary supply to the load,

means responsive to the energization of main supply for moving said mainswitch to the said one position and means responsive to deenergizationto said main supply for moving said switch to the other position, andmanually controlled means for actuating said switch for normallyconnecting the load to the auxiliary supply when the auxiliary supply isenergized and connecting the load to the main supply when the auxiliarysupply is deenergized.

8. A control system for connecting a load to a main or auxiliary sourceof power comprising switch means for selectively connecting one at atime said main or auxiliary source of power to said load, meansresponsive to the energization of said main source of power forconnecting said load to said main source of power, and means responsiveto the deenergization of said main source of power for disconnectingsaid load from said main source of power and connecting said load tosaid auxiliary source of power, manually controlled means for normallyactuating said connecting means for connecting said load to saidauxiliary source of power when said auxiliary source of power isenergized, said manually controlled means operating said connectingmeans for connecting said load to said main source of power when saidauxiliary source of power is deenergized, timing means for delaying thedisconnection of said load from said main and auxiliary sources of powerwhereby a momentary interruption in the energization of the loadconnected source of power will not operate said connecting means.

9. A control system for connecting a load to a main or auxiliary sourceof power comprising switch means for selectively connecting one at atime said main or auxiliary source of power to said load, meansresponsive to the energization of said main source of power forconnecting said load to said main source of power, and means responsiveto the deenergization of said main source of power for disconnectingsaid load from said main source of power and connecting said load tosaid auxiliary source of power, manually controlled means for normallyactuating said connecting means for connecting said load to saidauxiliary source of power when said auxiliary source of power isenergized, said manually controlled means operating said connectingmeans for connecting said load to said main source of power when saidauxiliary source of power is deenergized.

References Cited in the file of this patent UNITED STATES PATENTS1,528,045 Butcher Mar. 3, 1925 1,869,330 Anderson July 26, 19322,018,495 Hoffman Oct. 22, 1935 2,486,305 Mahnke Oct. 25, 1949

